The present invention is directed to a computer controlled apparatus for characterizing a plurality of organic or inorganic materials, and more particularly to a characterization apparatus that uses an electrically-driven sensor array to characterize a plurality of materials simultaneously and rapidly.
Companies are turning to combinatorial materials science techniques for developing new compounds or materials (including formulations, materials having different processing histories, or mixtures of compounds) having novel physical and chemical properties. Combinatorial materials science refers generally to methods and apparatuses for creating a collection of chemically diverse compounds or materials and to methods and apparatuses for rapidly testing or screening such compounds or materials for desired performance characteristics and/or properties. The collections of chemical compounds or materials are commonly called xe2x80x9clibrariesxe2x80x9d. See U.S. Pat. No. 5,776,359, herein incorporated by reference, for a general discussion of combinatorial methodologies.
A virtually infinite number of useful materials or compounds can be prepared by combining different elements of the Periodic Table of Elements in varying ratios, by creating compounds with different arrangements of elements, and by creating materials comprising mixtures of compounds or formulations with differing processing histories. Discovery of useful materials for a particular application may require preparation or characterization of many candidate materials or compounds. Preparing and screening a large number of candidates increases the probability of useful discoveries. Thus, any system that can analyze and characterize the properties of combinatorially prepared library members quickly and accurately is highly desirable.
Many conventional measurement systems comprise a distinct specialized machine for characterizing a particular material property, so that testing of a candidate material can use many machines and can be cumbersome and time-consuming. Also, most known materials characterization devices measure only one material sample at a time, severely limiting the number of samples that can be characterized per unit time.
Optical screening methods and devices have been preferred for many combinatorial chemistry and combinatorial materials science applications because they are non-contact and non-destructive. See for example WO 98/15805, incorporated herein by reference. For example, luminescence may be screened optically. When monitoring chemical reactions, for example, thermal imaging with an infrared camera can detect heat released during relatively fast exothermic reactions. See WO 98/15813, incorporated herein by reference. Although optical methods are particularly useful for characterizing materials or properties in certain circumstances, many materials characterization techniques are difficult or impossible to perform using optical methods. Therefore, there is still a need for a more direct materials characterization method that involves more intimate contact between the material samples and the sensing apparatus.
Conventional sensors that generate electrical data corresponding to material properties are typically designed as individual, discrete units, each sensor having its own packaging and wiring connections. Many materials characterization sensors are designed to be used individually in or with a machine that characterizes one sample at a time. Linking a plurality of these individual sensors in an array format, assuming that it is physically possible, would be expensive and often creates overly complicated wiring schemes with minimal gains in operating efficiency for the overall sensing system.
One structure using multiple material samples is a microfabricated array containing xe2x80x9cmicrohotplatesxe2x80x9d. The microhotplates act as miniature heating plates for supporting and selectively heating material samples placed thereon. U.S. Pat. No. 5,356,756 to Cavicchi et al and U.S. Pat. No. 5,345,213 to Semancik et al. as well the article entitled xe2x80x9cKinetically Controlled Chemical Sensing Using Micromachined Structures,xe2x80x9d by Semancik and Cavicchi, (Accounts of Chemical Research, Vol. 31, No. 5, 1998), all illustrate the microhotplate concept and are incorporated herein by reference. Although arrays containing microhotplates are known, they have been used primarily to create varied processing conditions for preparing materials. A need still exists for an array-based sensor system that can actually characterize material properties.
It is therefore an object of the invention to provide a materials characterization system that can measure properties of many material samples quickly, and in some embodiments simultaneously.
It is also an object of the invention to construct a materials characterization system having a modular structure that can be connected to a flexible electronic platform to allow many different material properties to be measured with minimal modification of the apparatus.
This invention provides an apparatus (or system) and method for testing materials in an array format using sensors that contact the materials being tested. Accordingly, the present invention is directed to an electronically-driven sensor array system for rapid characterization of multiple materials. A plurality of sensors are disposed on a substrate to form a sensor array. Properties that can be measured include thermal, electrical and mechanical properties of samples. Regardless of the property being measured or the specific apparatus, the materials characterization system of the invention includes multiple sensors carrying multiple samples, means for routing signals to and from the sensors, electronic test circuitry, and a computer or processor to receive and interpret data from the sensors. In a preferred embodiment, a modular system is constructed including a single sensor array format, and signal routing equipment compatible with this format which can be used with multiple sensor types and multiple electronic test equipment types, permitting maximum flexibility of the system while preserving the general advantages of sensor array-based characterization. Alternatively, some or all of the different parts of the system may be integrated together into a single physical component of the system.
The sensors can be operated in serial or parallel fashion. A wide range of electronically driven sensors may be employed, which those of skill in the art will appreciate provide the opportunity to design an apparatus or method for specific applications or property measurements. The environment in which the measurement is made by the sensor can be controlled.
This invention allows for rapid screening of combinatorial libraries or large numbers of samples prepared by other means. This invention allows for property measurements that cannot be done optically. However, optical measurements may be made in conjunction with the sensor based electronic measurements of this invention. One potentially important feature is the speed of the property measurements made with this invention. Two independent reasons for this speed are that one can measure samples in parallel or with smaller sample sizes than with conventional measurement techniques. Moreover, automated sample handling, array preparation and/or sensor operation allows for a completely automated rapid property measurement system in accord with this invention.
The materials characterization system of the present invention computer controlled. The control program includes a series of program instructions that implement and execute data gathering from the sensors, processing the data and making control decisions based on the data, supplying test equipment operational control instructions, performing signal processing operations on signals (data) gathered from the sensors, and calculating an arithmetic value for selected material properties based on the gathered and processed data from the sensors.
Further preferred embodiments are defined by the dependent claims 2 to 46.
Preferably, a microthin film membrane forming said sensors is a silicon nitride membrane, and said substrate supporting said silicon nitride membranes in said sensor array is a silicon wafer.
Preferably, at least one sensor in said sensor array comprises: a microthin film membrane supported by said substrate such that said sensor array is an array of microthin film windows; a first wire disposed on said microthin film membrane, said first wire acting as a heater and a first thermometer; and a second wire spaced apart from said first wire and disposed on said substrate, said second wire acting as a second thermometer.
Preferably, said microthin film membrane forming said sensors is a silicon nitride membrane, and said substrate supporting said silicon nitride membranes in said sensor array is a silicon wafer.
Preferably, said substrate is made of a polymer sheet, and said sensor array includes a plurality of heater/thermometers disposed on said polymer sheet.
Preferably, said polymer sheet is a polyimide.
Preferably, said heater/thermometer is printed on said polymer sheet via lithography.
Preferably, said substrate is made of a poor thermal conducting material that is at least 100 microns thick, and wherein said sensor array includes a plurality of heater/thermometers disposed on said material.
Preferably, said heater/thermometer is printed on a glass plate via lithography.
Preferably, said sensor array includes a plurality of thermometers disposed on a top surface of said substrate, and said substrate includes a large area heater disposed on a bottom surface of said substrate.
Preferably, said substrate is made of a polymer sheet.
Preferably, said substrate is made from a material having poor thermal conductivity and is placed on a heater block, and wherein said sensor array includes a plurality of temperature sensors disposed on the substrate such that a temperature difference between a first portion and a second portion of the substrate can be determined.
Preferably, said substrate is a glass plate.
Preferably, at least one sensor in said sensor array comprises: a sample support with a thermal measurement pattern disposed thereon; a gap between said sample support and said substrate for thermally isolating said sample support from said substrate; and a plurality of bridges connecting said sample support to said substrate over said gap.
Preferably, said leads are deposited on said substrate, and wherein said material samples in said materials library are deposited on top of said leads.
Preferably, said material samples in the materials library are deposited on said substrate, and said leads are deposited on top of said samples.
Preferably, a generating means comprises a magnet that generates a magnetic field over the entire sensor array.
Preferably, said generating means comprises a magnet array having a plurality of magnets arranged in the same format as said sensors in said sensor array, wherein each magnet in said magnet array corresponds with a sensor in said sensor array to generate a magnetic field over the corresponding sensor.
Preferably, said sensors in said sensor array further measure temperature, and said apparatus further comprises a plurality of temperature controlled elements to impose a temperature gradient across at least one sample in said sensor array.
Preferably, at least one sensor in said sensor array comprises interdigitated electrodes disposed on said substrate.
Preferably, at least one sensor in said sensor array comprises: a mechanical resonator formed on said substrate; and a piezoelectric material deposited on top of said sensor to form an acoustic wave sensing electrode.
Preferably, said acoustic wave sensing electrode is operable in at least one of a surface acoustic wave resonance mode, a thickness shear mode, and a flexural plate wave resonance mode.
Preferably, said acoustic wave sensing electrode acts as both a mechanical resonator and a materials characterization device.
Preferably, at least one sensor in said sensor array comprises interdigitated electrodes disposed on said substrate.
Preferably, at least one sensor in said sensor array comprises: a mechanical resonator formed on said substrate; and a piezoelectric material deposited on top of said sensor to form an acoustic wave sensing electrode.
Preferably, said acoustic wave sensing electrode is operable in at least one of a surface acoustic wave resonance mode, a thickness shear mode, and a flexural plate wave resonance mode.
Preferably, said acoustic wave sensing electrode acts as both a mechanical resonator and a materials characterization device.
Preferably, the cantilever sensor is attached to a piezoresistor such that a deflection amount of said cantilever sensor is detected by a change in a resistance value of the piezoresistor.
Preferably said sensors in said sensor array are arranged in a format compatible with combinatorial chemistry instrumentation.
Preferably, said sensor array is an 8xc3x978 array with a 0.25 mm pitch.
Preferably, said sensor array is an 8xc3x9712 array with a 9 mm pitch.
Preferably, said sensor array is a 16xc3x9724 array.
Preferably, said sensors in said sensor array are disposed on said substrate in a planar arrangement.
Preferably, said sensors in said sensor array are attached to said substrate via a plurality of sensor plates disposed in an array format and extending generally perpendicularly from said substrate.
Preferably, said plurality of sensors in said sensor array are arranged in a geometric shape.
Preferably, said geometric shape is a closed shape having straight sides.
Preferably, said geometric shape is a closed shape having curved sides.
Preferably, said geometric shape is a closed shape having both straight and curved sides.
Preferably, said geometric shape is an open shape having straight sides.
Preferably, said geometric shape is an open shape having curved sides.
Preferably, said geometric shape is an open shape having both straight and curved sides.
Preferably, said sensor array contains at least 48 sensors.
Preferably, said sensor array contains at least 96 sensors.
Preferably, said sensor array contains at least 128 sensors.
Preferably, said sensor array contains between 5 and 400 sensors.
Preferably, said circuit board in said standardized interconnection device and said sensor array are coupled together via a connector, said connector being one selected from the group consisting of conducting elastomeric connectors, conducting adhesives, cantilever probes, stick probes, wafer-to-board bonding, solder bump bonding, wire bonding, spring loaded contacts, soldering, and direct pressure connection between contact pads.
Preferably, said circuit board and said sensor array are coupled through one selected from the group consisting conducting elastomeric connectors, conducting adhesives, cantilever probes, stick probes, wafer-to-board bonding, solder bump bonding, wire bonding, spring loaded contacts, soldering, and direct pressure connection between contact pads.
Preferably, said link is a multi-wire cable.
Preferably, said link is a wireless connection.
Preferably, said interconnection device comprises a signal routing means for selectively coupling a sensor or a group of sensors in said sensor array to said electronic platform such that said electronic platform sends signals to and receives signals from said sensor array via said signal routing means.
Preferably, said link is a multi-wire cable.
Preferably, said link is a wireless connection.
Preferably, said interconnection device comprises a signal routing means for selectively coupling a sensor or a group of sensors in said sensor array to said electronic platform such that said electronic platform sends signals to and receives signals from said sensor array via said signal routing means.
Preferably, the computer is managed by software that controls data collection, data viewing, and user interface.
Preferably, said signal routing means selects a group of two or more sensors at a time for simultaneous analysis, and the apparatus further comprises two or more electronic channels connecting each of said group of sensors to said electronic test circuitry, the number of electronic channels being equal to the number of sensors in said group by said signal routing means.
Preferably, said automated material dispensing device are arranged in a format compatible with combinatorial chemistry instrumentation.
Preferably, said automated material deposition device employs a method selected from the group consisting of sputtering, electron beam evaporation, thermal evaporation, laser ablation and chemical vapor deposition.
Regarding the method of the present invention, further preferred embodiments are defined in the dependent claims 48 to 69.
Preferably the depositing step includes placing at least one material on each sensor by vapor deposition to create the samples.
Preferably, the vapor deposition method is a combinatorial vapor deposition method that deposits two or more materials in varying proportions on different sensors in the sensor array.
Preferably, the depositing step further includes the step of heating the samples on the sensor array after they are placed on the sensors by vapor deposition.
Preferably, the environment that is changed is at least one selected from the group consisting of humidity, temperature, pressure, illumination, irradiation, magnetic field and atmospheric composition.
Preferably, the input signal transmitted in the transmitting step is a combination of a linear ramp signal and a modulated AC signal superimposed on the linear ramp signal, and wherein the monitoring step monitors a modulation amplitude in the output signal and an average value of the output signal.
Preferably, at least one sensor in the sensor array has a heater portion and a thermometer portion, the combined linear ramp signal and modulated AC signal is transmitted through the heater portion, a DC signal is transmitted through the thermometer portion, and wherein the modulation amplitude in the output signal corresponds with a heat capacity of the sample and the average value of the output signal corresponds with an average temperature of the sample.
Preferably, the transmitting step transmits a linear ramp signal and an AC sinusoidal signal, and wherein the monitoring step monitors an output signal.
Preferably, at least one sensor in the sensor array has a heater portion and a thermometer portion, the linear ramp signal is transmitted through the heater portion and the AC signal is transmitted through the thermometer portion.
Preferably, a first frequency component of the output signal corresponds with the average temperature of the sample and wherein a second frequency component of the output signal corresponds with the heat capacity of the sample.
Preferably, the loss of mass in the sample is due to at least one selected from the group consisting of decomposition, burning, and outgassing of reaction products.
Preferably, the measuring step measures a difference between the sample on the top surface of the substrate and a bottom surface of the substrate, wherein the temperature difference corresponds to the heat capacity of the sample.
Preferably, the heating step comprises the step of increasing the temperature applied to the bottom surface of the substrate at a measured rate, and wherein the measuring step comprises the step of comparing the rate at which the sample temperature increases and the measured rate at the bottom surface of the substrate.
Preferably, the measuring step measures a difference between the first portion of the substrate and a second portion of the substrate, wherein the temperature difference corresponds to the heat capacity of the sample.
Preferably, the heating step comprises the step of increasing the temperature applied to the first portion of the substrate at a measured rate, and wherein the measuring step comprises the step of comparing the rate at which the sample temperature increases and the measured rate at the first portion of the substrate.
Preferably, the method further comprises the step of measuring a temperature of the sample.
Preferably, the temperature and the complex impedance of the sensor are measured simultaneously.
Preferably, at least one sensor in the sensor array is a mechanical resonator, wherein the depositing step includes depositing a sample material on the mechanical resonator and wherein measuring step includes the step of transmitting an input signal to said at least one sensor to operate the sensor in a resonance mode, and wherein the monitoring step includes the step of measuring a resonator response.
Preferably, at least one sensor in the sensor array is a mechanical resonator, wherein the depositing step includes depositing a sample material on the mechanical resonator, and wherein the measuring step includes the steps of: placing the sensor array in a magnetic field; and
generating a resonance signal in the mechanical resonator; measuring an amount of damping in the resonance signal, wherein the damping amount corresponds with the sample material""s response to the magnetic field.
Preferably, at least one sensor in the sensor array is a mechanical actuator, wherein the depositing step includes depositing a sample material on the mechanical actuator and wherein the monitoring step includes the step of measuring an actuator response.
Preferably, at least one sensor in the sensor array is a mechanical actuator, wherein the depositing step includes depositing a sample material on the mechanical actuator, and wherein the measuring step includes the steps of: placing the sensor array in a magnetic field; measuring an amount of displacement in the mechanical actuator, wherein the displacement amount corresponds with the sample material""s response to the magnetic field.
Preferably, the measuring step includes the steps of: passing current through at least one sample; and measuring a voltage across the sample to obtain the resistance of the sample.
Preferably, the measuring step includes the steps of: placing the sensor array in a magnetic field; passing current through at least one sample; and measuring one or more voltages across the sample to obtain either a Hall resistance, a magnetoresistance of the sample or both.
Preferably, the measuring step includes the steps of: heating or cooling one portion of at least one sample; measuring a first temperature at the first portion of the sample and a second temperature at a second portion of the sample; and calculating a temperature difference between the first temperature and the second temperature, wherein the temperature difference corresponds with a thermal conductivity of the sample.
Preferably, the heating step includes placing a heater or cooler at one portion of the sensor array such that the sensor array has a heated or cooled portion and a non-heated or non-cooled portion.
Preferably, the heating or cooling step includes placing a heater or cooler at each sensor such that each sensor has a heated or cooled portion and a non-heated or non-cooled portion.
Preferably, the method further comprises the step of placing the sensor array in a vacuum.
Preferably, the method further comprises heating or cooling one portion of at least one sample;
determining a first temperature at the first portion of the sample and a second temperature at a second portion of the sample; and measuring a voltage difference across the sample, wherein the voltage difference and the temperature difference corresponds with a thermopower of the sample.
Preferably, at least one sensor in the sensor array is a Hall effect sensor, and wherein the measuring step comprises the steps of: placing the sensor array in a magnetic field;
measuring a response of at least one Hall effect sensor; and comparing the response of said at least one Hall effect sensor containing a sample with a reference Hall effect sensor that does not contain a sample deposited thereon.
Preferably, at least one sensor in the sensor array is a cantilever sensor, and wherein the measuring step comprises the steps of: placing the sensor array in a magnetic field; and measuring an electrical signal corresponding to said at least one cantilever sensor, wherein the electrical signal corresponds to a deflection amount of the cantilever sensor and the magnetic property of the sample material disposed on the cantilever sensor.
Preferably, the transmitted signal comprises a step or pulse and the measurement step comprises monitoring the temperature change of the sample in response to the stepper pulse, and determining a thermal time constant.
Preferably, a single wire acts as both the thermometer and heater.
Preferably, the transmitting step transmits a linear ramp signal and an AC sinusoidal signal, and wherein the monitoring step monitors an output signal.
Preferably, a first frequency component of the output signal corresponds with the average temperature of the sample and wherein a second frequency component of the output signal corresponds with the heat capacity of the sample.